The plot, if it ever existed at all, is about a Christian and an atheist arguing back and forth on morality and God’s existence. This is coloured by Sade’s bad personal experiences not just in school but also because his uncle was an abbot who participated in very sinful practises. Said uncle was also a bad influence on the young Sade.
It allegedly inspired a scene in the film Nazarin and its director Luis Bunuel is no stranger to adapting portions of Marquis de Sade’s other works and even included him in one of his films. Since Sade wrote really graphic stories, it’s one of the tamer ones out there but could offend certain sensibilities as Sade distrusted organised religion ever since and is very vocal about it.